Accuracy change with Altitude change.

Another thought...I have a few friends who have built small buildings...15' by 15 ' maybe....heated....all of thier loading equipment, bench, electricity...everything you would need are inside. They built it to shoot in the winter. LUCKY BASTARDS

Now, someone please explain to me how groups would change SIZE when shooting from inside the heated room to 1000 yards when it is -20F, +20F, 65F... outside. What factor, exactly, would cause groups to change size. How about BARO....what would change the groupe SIZE with a change in Baro PSI?

On my shooting solution exl worksheet I have Temp as first column, 10 degree increments! Because at 70F the ammo flys at 3,080 and at Zero F it leaves at 2,997 {-83fps}I have calibrated all inf so all I need to set my scope to optimum power setting {Zeiss: rapid Z 800} is Temp - Alt - Yards to target and last but not least - Wind.

Don't have any knowledge of the temp causing POI to grow but mine just drops like you would expect with speed reduction. However, I would expect, as already stated, in some cases your group could very well - in some guns- increase or decrease. Remember it's Nellie not Fred!